Add esign to document signatures

Employee document signatures recorded an acknowledgment with no
cryptographic proof, unlike document approvals which already create
and accept an electronic signature on every decision.

Mirror the approval flow on the sign path: generate the signed
document PDF, create-and-accept an esign record, and persist its id
on the document_version_signatures row through a new
electronic_signature_id column. Capture the signer IP and user agent
in the resolver, and re-check the published/archived preconditions
inside the transaction so the seal cannot race document state.

Make the consent wording a single backend source of truth shared by
the text that is sealed and the text shown in the UI. Define
DocumentSignatureConsentText and DocumentApprovalConsentText in the
probo service package and the NDA copy in the trust service, each
owned by the flow that uses it, and stop esign from appending the
generic clause to caller-provided consent text so approvals no
longer seal a duplicated sentence.

Expose the resolved consent text through GraphQL on
EmployeeDocumentVersion and DocumentVersionApprovalDecision, and have
the signing, approval, and NDA pages render it from the API instead
of hard-coded strings, mirroring how the NDA page already worked.

Align the wording with the actual interaction: the buttons read
"Review and sign" and "Review and approve", the clauses reference
those actions, and the inaccurate "typing my full name" phrasing is
removed everywhere.

Signed-off-by: Sacha Al Himdani <sacha@getprobo.com>

pkg/coredata/migrations/20260610T992900Z.sql

@@ -0,0 +1,16 @@
+-- Copyright (c) 2026 Probo Inc <hello@probo.com>.
+--
+-- Permission to use, copy, modify, and/or distribute this software for any
+-- purpose with or without fee is hereby granted, provided that the above
+-- copyright notice and this permission notice appear in all copies.
+--
+-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+-- REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+-- AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+-- INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+-- LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+-- OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+-- PERFORMANCE OF THIS SOFTWARE.
+
+ALTER TABLE document_version_signatures
+    ADD COLUMN electronic_signature_id TEXT REFERENCES electronic_signatures(id) ON DELETE RESTRICT;